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Hipockets

Serratolamna koerti ?

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Hipockets

I found this a while ago on a spoil island in the Cape Fear River in Wilmington, NC . I believe this is mostly Castle Hayne formation, eocene. Tooth is 1 1/4 inches long. Missing a side cusp, no serrations, no nutrient groove that I see . Is this a Serratolamna koerti ? Thanks for your help.

20180213181729.jpg

20180213181806.jpg

20180213181946.jpg

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Plax

Wow! Can't confirm the ID but wouldn't rule out Paleocene either if it's from .... Lots of Bald Head shoals Formation there but have never seen anything but mollusks from it.

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Tidgy's Dad

That's a smashing tooth! :wub:

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Plax

looks like the pic in the NCFC Fish volume. There are a couple of Southeastern Geology (Duke) papers on the dredge geology of the lower Cape Fear River. I only have paper (no pdf) but could dig a copy out for you so you can figure what's on your island.

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sixgill pete

Looking at the pics, I would agree that it is S. koerti. But Plax did make a very interesting point about the Bald Head Shoals Formation.

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Harry Pristis

 

I think these teeth from the Late Eocene Ocala Group Limestone are Serratolamna koerti.  

 

 

serratolamnaFlorida.jpg

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Hipockets

Thanks everyone.

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siteseer
On 2/14/2018 at 5:20 AM, Plax said:

Wow! Can't confirm the ID but wouldn't rule out Paleocene either if it's from .... Lots of Bald Head shoals Formation there but have never seen anything but mollusks from it.

 

There really isn't anything from the Paleocene that has a tooth form like the one in question.  I also think it's S. koerti.  It has a broad-based, less-tapering crown as in S. koerti upper anteriors with rather short root lobes.  The crown is also rather flat as seen in S. koerti.

 

I have read that at least two researchers would reassign koerti to Carcharias (Parmley, Cicimurri, and Campbell, 2003) but I think their argument would be more convincing if they had figured specimens representative of at least a few jaw positions (upper anterior, upper lateral, lower lateral,etc.) and then defended their assignment to Carcharias.  Other than Middle Eocene Striatolamia, you don't see many other Carcharias species with such broad-based anterior crowns.  I must add that there is a reasonable argument to reassign Striatolamia striata and S. macrota to Carcharias although you don't hear about that much anymore. 

 

Teeth of koerti don't appear to be common anywhere except perhaps Togo (appears to have been a warm-water species so it makes sense it would be more common in an equatorial area) so no one has really put together even a partial dentition as far as I know though I'm sure some collectors have played with the idea.

 

PARMLEY, D. & CICIMURRI, D.J. & CAMPBELL, B. (2003)
Late Eocene sharks of the Hardie Mine local fauna of Wilkinson County, Georgia. GEORGIA JOURNAL OF SCIENCE, 61 (3): 153–179.

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Anomotodon
6 hours ago, siteseer said:

I must add that there is a reasonable argument to reassign Striatolamia striata and S. macrota to Carcharias although you don't hear about that much anymore. 

 

I disagree. Striatolamia macrota coexisted with at least two actual Carcharias species C. accutissima and C. (Sylvestrilamia) teretidens. Both of them are generally similar to modern C. taurus, except more striated S. teretidens teeth, while different from Striatolamia (A comparison of isolated teeth of early Eocene Striatolamia macrota (Chondrichthyes, Lamniformes), with those of a Recent sand shark, Carcharias taurus.): anteriors are more or less comparable, however Eocene Carcharias have taller cusplets, finer striations and wider root lobes; but laterals are totally different: sharper cusplets compared to broad Striatolamia cusplets, much more mesio-distally compressed crowns, more compressed root lobes, etc. 

In Kyiv Eocene though most common Striatolamia morph is more massive than in Cunningham. Unfortunately, don't have good pictures of my specimens, especially of Carcharias.

So, here is what I think about this systematic issue: in Danian early S. striata diverged from early striated Carcharias species similar to Carcharias sp. B in Welton & Farish (K/T extinction may account for increased lateral broadness and average size in S. striata, because many large lamniform species became extinct) while actual Carcharias species similar to non-striated C. accutissima appeared earlier in the Cretaceous from late Eostriatolamia (?), then early Gluekmanotodus, Jaekelotodus and Hypotodus (=Carcharias hopei and definitely not actually Carcharias) losing striations independently  from Cretaceous Carcharias and becoming top predators with completely cutting tooth morphology appeared somewhere in Thanetian-Selandian, in Eocene S. macrota replaced S. striata and coexisted with now more diverse Jaekelotodontids (+Mennerotodus, Borealotodus,...) before all becoming extinct in Priabonian-Rupelian event. Therefore, modern Carcharias line diverged from Striatolamia in Cretaceous, so I don't think it is right to consider them synonymous. However, above was mostly my personal opinion.

An important thing to mention is that before jumping into any conclusions we need to wait for the revision of Eocene "Odontaspididae" and "Jaekelotodontidae" 

 

image.png.c1258527184cacfb120f7b238d3afc28.png

 

S. macrota Kyiv Eocene

Anterior

0001-001_768.jpg?height=760&width=926

Lateral

0900-002_980.jpg?height=520&width=980

 

C. (S.) teretidens

4250-001_980.jpg?height=700&width=980

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Anomotodon

Sharks are fun indeed, especially sand tigers :meg:

My primary argument here was evolutionary. You are right that differences are mostly quantitative rather than qualitative, but isn't it the same with most shark teeth species in the same family? Same with any fossil species: without any obvious evidence of reproductive isolation (and therefore biological species concept) species and genus borders are subjective. Yet Carcharias lateral teeth are different from late S. macrota in the ecological aspect: a trend in Striatolamia evolution is increase in lateral tooth width - transition to 'cutting' morphology that was most prominent in Middle-Late Eocene specimens (like in Kyiv).

Forgot to mention about this in the previous post. Cunningham teeth are somewhat closer to Carcharias and S. striata than mine because they are Ypresian. Also comparisons with Eocene Carcharias like C. accutissima are obviously more valuable in the question of Striatolamia genus identity than with modern C. taurus.

"Teeth of Early Eocene members of S. macrota (Agassiz, 1843) differ in size and morphology from those of Middle Eocene age. Those from the Early Eocene have been referred to as Striatolamia striata or S. elegans (White, 1931: 38; Casier, 1966: 69; Arambourg 1952: 62). Zhelezko and Kozlov (1999) designated a series of species and subspecies of Striatolamia spanning the late Paleocene to the Late Eocene, distinguished by characters on the upper lateral teeth. These were principally adult size, crown shape, degree of separation of the lateral cusps and the amount and nature of the labial crown striation. The Ypresian representative in this series was Striatolamia elegans, with two subspecies; S, elegans naja in the early Ypresian and S. elegans elegans for the late Ypresian. Lacking formal descriptions, both subspecies are nomena nuda."
Malyshkina & Ward, 2016

So, what I suggested before is that it seems that Carcharias sp. B from Texas Maastrichtian (Welton & Farish, 1993)-S. striata-S.macrota form a continuous line with trends with ecological implications 1) size increase 2) broadness of lateral teeth and cusplets. 3) decrease in anterior cusplet height 4) decrease in striation density. I don't know when the line  of smaller sand tigers C. accutissima-C.cuspidata-C.taurus (approximate) diverged from large Maastrichtian Carcharias, but anyway we have 35 my between large striated Maastrichtian Carcharias and last Striatolamia. A Carcharias-Striatolamia boundary can be placed anywhere yet somewhere along this line there was an ecological transition to a large pelagic predator.

Also, anterior cusplet height in late Striatolamia is much shorter than in modern C. taurus and a usual trend in shark tooth evolution is opposite - decrease in cusplet size, so it is likely a side lineage compared to Carcharias accutissima-cuspidata-taurus.

 

Unfortunately, I haven't found any newer literature on  Striatolamia tooth variation than two papers you cited that place S. macrota to C. macrota. Personally, I doubt that degree of variation of striations and cusplets in Striatolamia is significant since the study of variation in Antarctic specimens is relatively old and many aspects of shark systematics changed since then. Most importantly, at least Hypotodus and potentially Borealotodus had very similar anteriors that could have been confused with Striatolamia by the authors and they lack striations and have taller cusplets. 

There definitely were many distinct species of odontaspidids in Eocene, so a new revision assessing degrees of intraspecific variation would be very helpful.

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siteseer
On February 20, 2018 at 12:16 AM, Anomotodon said:

Sharks are fun indeed, especially sand tigers :meg:

My primary argument here was evolutionary. You are right that differences are mostly quantitative rather than qualitative, but isn't it the same with most shark teeth species in the same family? Same with any fossil species: without any obvious evidence of reproductive isolation (and therefore biological species concept) species and genus borders are subjective. Yet Carcharias lateral teeth are different from late S. macrota in the ecological aspect: a trend in Striatolamia evolution is increase in lateral tooth width - transition to 'cutting' morphology that was most prominent in Middle-Late Eocene specimens (like in Kyiv).

Forgot to mention about this in the previous post. Cunningham teeth are somewhat closer to Carcharias and S. striata than mine because they are Ypresian. Also comparisons with Eocene Carcharias like C. accutissima are obviously more valuable in the question of Striatolamia genus identity than with modern C. taurus.

"Teeth of Early Eocene members of S. macrota (Agassiz, 1843) differ in size and morphology from those of Middle Eocene age. Those from the Early Eocene have been referred to as Striatolamia striata or S. elegans (White, 1931: 38; Casier, 1966: 69; Arambourg 1952: 62). Zhelezko and Kozlov (1999) designated a series of species and subspecies of Striatolamia spanning the late Paleocene to the Late Eocene, distinguished by characters on the upper lateral teeth. These were principally adult size, crown shape, degree of separation of the lateral cusps and the amount and nature of the labial crown striation. The Ypresian representative in this series was Striatolamia elegans, with two subspecies; S, elegans naja in the early Ypresian and S. elegans elegans for the late Ypresian. Lacking formal descriptions, both subspecies are nomena nuda."
Malyshkina & Ward, 2016

So, what I suggested before is that it seems that Carcharias sp. B from Texas Maastrichtian (Welton & Farish, 1993)-S. striata-S.macrota form a continuous line with trends with ecological implications 1) size increase 2) broadness of lateral teeth and cusplets. 3) decrease in anterior cusplet height 4) decrease in striation density. I don't know when the line  of smaller sand tigers C. accutissima-C.cuspidata-C.taurus (approximate) diverged from large Maastrichtian Carcharias, but anyway we have 35 my between large striated Maastrichtian Carcharias and last Striatolamia. A Carcharias-Striatolamia boundary can be placed anywhere yet somewhere along this line there was an ecological transition to a large pelagic predator.

Also, anterior cusplet height in late Striatolamia is much shorter than in modern C. taurus and a usual trend in shark tooth evolution is opposite - decrease in cusplet size, so it is likely a side lineage compared to Carcharias accutissima-cuspidata-taurus.

 

Unfortunately, I haven't found any newer literature on  Striatolamia tooth variation than two papers you cited that place S. macrota to C. macrota. Personally, I doubt that degree of variation of striations and cusplets in Striatolamia is significant since the study of variation in Antarctic specimens is relatively old and many aspects of shark systematics changed since then. Most importantly, at least Hypotodus and potentially Borealotodus had very similar anteriors that could have been confused with Striatolamia by the authors and they lack striations and have taller cusplets. 

There definitely were many distinct species of odontaspidids in Eocene, so a new revision assessing degrees of intraspecific variation would be very helpful.

 

Well, it looks like I'm being overwhelmed by facts and I'm the only one left still wondering if Striatolamia is valid.  Thanks for the info.

 

I would assume Striatolamia diverged in the Danian as sharks were beginning to radiate after the K-T extinctions.  I don't have much from the Danian in terms of specimens as I've never collected it.  There aren't too many shark-bearing sites in the US.  Offhand, I recall there's a site around Benton, Arkansas and sites in New Jersey.  I'm told there's an early Otodus in the Danian.  I'd have to check my files.

 

Yes, there's a Late Maastrichtian deposit in Texas (Kemp Clay) with a rich fauna including micros so a sample of those teeth compared with a good Danian sample (Morocco, Denmark, Russia) would be a great paper.

 

Jess

 

 

 

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